In recent weeks, you may have trouble logging in to your online PNC bank account. PNC has recently apologized to customers, saying that during high traffic times, users may have been automatically blocked. This is due to efforts to thwart cyber-attacks, namely denial-of-service attacks. This type of cyber warfare isn’t necessarily hacking, but involves saturating a server with traffic, causing the server to overload.

PNC said they have been hit by occasional denial-of-service attacks since Dec. 10, when a hacking group called Cyber Fighters announced they would be targeting several large U.S. banks. The U.S. government believes this group to be based in Iran, but has produced no evidence to the claim. PNC insisted that their website and its information has sophisticated encryption and that all customers’ information is protected.